hanging up calls

Hi there I don't have an issue with this I just do a double tap with two fingers and it hangs up fine.

With my IPhone 5S, using the lock button only works if I have the phone to my ear. If I take the phone away from my ear and press the lock key, it just locks the phone and doesn't hang up. Perhaps the same is true with the IPhone 6?

I don't know. With previous iPhones, yes you can end a call with the power button. Like John said in post above you have to have it by your ear, this triggers the proximity sensor in the top of the screen to darken the screen and move audio to the earpiece. I had issues with two finger double tapping in early versions of 8.0 or 8.1 a while ago, so I don't even do that anymore. I just find the accept button and go from there.
I've heard other people say that no, you can't end a call on the 6 with the power button. However, I am not sure if this is only on speaker or if it is up to your face.
HTH

Instead of pressing and releasing, give it a half second, then let go. Maybe that's it. I remember showing a friend, hey I think I can hang up withthe power buttos, watch. I guess I had an itchy finger, because I wadn't intended on showing her right then. click. Oops? sorry! Lol.

The two finger double tap gesture usually works for me to hang up calls, when my phone's unlocked. I take it away from my ear, and perform the gesture, but sometimes I have to do it twice to get it to work.
The gesture hasn't worked to answer calls though last I tried it. Also, I'm not sure the lock button works to end calls, haven't tried it on my iPhone 6.

I don't have an IPhone6 but previous threads that have come up on this issue suggests that you can't end a call with the power button anymore via IPhone6.